Jenesis 1.0

DOOM is one of the oldest FPSes in existence, and its engine is famously so robust that it can run on pretty much anything and also create pretty much anything.  From FPSes to RPGs to companions to a city living game, it has a ton of different mods and maps that can all do different things. There are even full campaigns created called megawads. One of many is Jenesis.

To install Jenesis, you need to have ZDoom and move the WAD file into the GZDoom folder, which is pretty par for the course for DOOM maps.

This set of maps has a very straightforward story that doesn't exactly break the mold when it comes to DOOM stories. You follow a space marine dispatched to the familiar locale of Phobos to deal with a demon invasion. From there, you fight your way across the moon, make your way to Deimos, and then teleport into Hell to take out the demon Baphomet.

The maps aren't very long, with only a few maps passing "medium-size". Most of these maps have monster counts numbering 200 or lower, which is on the low side. You'll also get a feel of map flow, as they are all designed by the same person, which leads to similar tricks used on a number of maps such as constantly leading back to a constantly expanding common area.

Overall, Jenesis is one of the best-known megawad in the DOOM community for a good reason. It's well put together and also fun to play through.